Pressure mounted quartz oscillator



Jam 15, 1946. FQ- MORSE` 2,392,993

PRESSURE MOUNTED QUARTZ OSCILLATORS Filed May 6, 1944 20 jg 21 Y 31 g16; mmvron.

Samir Morse use.

Patented Jan. is, 194s PRESSURE MOUNTED QUARTZ OSCILLATOR Louis R.Morse, New York, N. Y., assignor, by

mesne assignments, to Empire Electronics Corporation, New York, N. Y.

Application May 6, 1944, Serial No. 534,404

6 Claims.

The invention relates to piezo-electric oscillator mountings of thepressure air gap type. Proper operational characteristics of anoscillator plate assembly of this general type are dependent upon themaintenance of uniform contact pressure and good electrical contacts.The invention is directed particularly to improvements in mountingconstructions affecting these features and adapted to enhance thedependability and faithfulness i oi performance over extended periods oftime and Quartz oscillator plates are seldom absolutely flat and usuallyhave a convex contour, and accordingly the marginal pressure areas liein different planes- When such a crystal is placed between twoelectrodes even though they have been lapped to exact flatness, they donot present a perfect contact to the oscillator plate at all of theintended pressure points. Furthermore, even if the original contactsprovided on assembly be uniform and adequatethese frequently changeduring usage due to various factors. For example, the metal electrodesmay become distorted by temperature changes or age, with resultantdeparture from uniform contact pressure and dis@ turbance of thefunctional characteristics of the oscillator plate, Also, vibrationfailure in quartz oscillator plates occasionally results fromdisplacement or shifting of the quartz with respect to the electrodes,or displacement of the electrodes and quartz assembly, causingvariations in contact pressure and contact resistance. The departuresfrom uniformity in turn result in erratic activity response anddisturbance of the functional characteristics of the oscillator plate ingeneral.

A condition which is particularly disturbing to the operationalcharacteristics is the development of increased electrical contactresistance which may result not only from loose contacts but is oftenaugmented by oxidation or corrosion. The quartz plate itself is subjectto decomposition and, together with the vibration, may tend to form amicroscopic film of quartz powder, increasing the contact resistance tothe mother quartz.

In accordance with the principles of the present invention, thedifilculties discussed are obvi-- ated by a self-adjusting springpressure electrical contact means adapted to exert a constant pressureat the several marginal supporting points regardless oi' any normaldistortion of the electrode plates or assembly and to provideself-cleaning electrical contactsA `which continue to penetrate to thesolid mass of the quartz plate.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises the features of construction,combination of elements, and arrangement oi.' parts, which will beexemplified in the construction hereinafter set forth. and the scope ofwhich invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the inventionreference should be had to the following detailed description taken inconnection with the accompanying drawing, in which:

Fig. 1 is a cross-sectional View, taken on the line i-i of Fig. 2, of ageneral. assembly of an oscillator plate embodying the invention;

Fig. 2 is an elevational view with parts of the casing broken away;

Fig. 3 is a perspective of one of the electrode plates;

Fig. 4 is a perspective of one of the auxiliary plates; and

Fig. 5 is a cross-sectional view of some of the elements taken on theline 5--5 of Fig. 2.

The invention is capable of incorporation in various conventional typesof quartz oscillator plate assembliesy the one shown in Fig, l beingillustrative. The crystal employed may likewise be of variousconventional shapes. but as shown in Fig, 1, comprises a thin fiat plateI il having a shape which in plan is square or rectangularwith'accordingly four right-angled corners. The crystal is sandwichedbetween two metal electrode plates Ii and i2, the face of each electrodeadjacent the crystals having lands or elevated corner areas i3 as shownparticularly in Fig. 3. Accordingly, the crystal is provided with airgaps i4 and I5 at its opposite sides throughout the central areathereof. The dimensions are somewhat exaggerated in Fig. 1, and it willbe understood that although the air gap thickness may vary underdifferent circumstances, it normally Would be within a. range of a fewthousandths of an inch.

Located adjacent to the surface of each electrode plate opposite to thecrystal is an auxiliary plate i8, I9 details of one of these being shownin Fig. 4. These plates may conveniently be formed by stamping from thinflexible electrical` conducting material, such as sheet metal. The.specific construction of each of these auxiliary plat includes acentral area 20 relatively thicker than the surrounding annular area.Spaced around the periphery of the body portion is a series of fingers2| each having an outer end bent at right anales to the main portionprovided with relatively sharp extremities 22. 'I'hese lingers arespaced similarly to, and correspond in number with, the supporting landsI2 o! the metal elec trode plates Il and I2. The extremities 22 areadapted to engage directly the crystal I0. To this end, the lands I3 maybe provided with open ings 25 through which project the respective iin-Sers 2 I.

The main casing or support 26 of electrically insulating material alsohas therein suitable electrical contacts such as the plates 21 and 28 inelectrical connection respectively with the terminals 29 and 30. Theoscillator plate assembly is adapted to be mounted in compressedrelation between the plates 21 and 28, and for this purpose there isshown the spring 3| adapted to urge the plates into pressure contactagainst plate 28. The fingers of the auxiliary plates I8 and I9 arelonger than the thickness of the plates Il and I2 at the, lands I3,^sothat under the pressure of the spring 3| the central areas 20 arepressed into firm engagement with the respective electrode plates Ii andi2 and the fingers 2| are each resiliently pressed into engagementdirectly with the crystal i forming a direct electrical contacttherewith. Since the ends of the fingers 2| in contact with theoscillator plates Iii are of limited area and under constant resillentpressure, they are, so to speak, self-cleaning and penetrate tothe solidquartz plate and continue to do so under extended usage regardless ofany amount of distortion of the metal electrodes II and I2 or relativedisplacement oi the plate elements which may occur over a period oftime. The operating characteristics of the assembly as a wholeaccordingly remain constant and uniform.

The auxiliary spring contact plates I8 and I8 are readily insertable orremovable, and are relatively thin, and, therefore, may be omitted forpreliminary tests in the lapping of the oscillator plate and othernishing or adjusting operations, and the spring plates thereafterinserted in the final assembly.

Since certain changes may be made in the above construction anddifferent embodiments of the invention could be made without departingfrom the scope thereof, it is intended that all matter contained in theabove description or shown in the accompanying drawing shall beinterpreted as illustrative and not in a limiting sense.

Having described my invention, what I claim as new and desire to secureby Letters Patent is:

l, In a piezo-electric oscillator assembly having a crystal and plateelectrode arranged in contacting relation therein, an auxiliary plate ofelectrically conducting material arranged adjacent said electrode on theside opposite to said crystal, and spring means for urging saidauxiliary plate, electrode and crystal into contact, said auxiliaryplate having spaced fingers at the outer edge adapted resiliently toengage respectiveb7 marginal portions of said crystal and to maintaindirect electrical contact therewith.

2. In a piezo-electric oscillator assembly having a support and acrystal sandwiched between a pair of electrodes therein, an auxiliaryplate of electrically conducting material arranged adjacent t he surfaceof each electrode on the side respectively opposite to the crystal, andspring means for compressing into contact said auxiliary plates,electrodes and crystal. said auxiliary plates each having spaced fingersat the outer edge adapted resiliently to engage respectively marginalportions of said crystal and to maintain direct electrical contacttherewith.

3. A piezo-electric oscillator assembly comprising a casing, a platecrystal and a plate electrode therein arranged to contact at marginalportions with an air gap at their central portions, an auxiliary plateof resilient electrically conducting material arranged adjacent saidelectrode opposite to the crystal, and spring pressure means forcompressing-said auxiliary plate, electrode and crystal, said auxiliaryplate having spaced bent finger portions adapted resiliently to engagedirectly said crystal at marginal points.

4. In a piezo-electric oscillator assembly having a crystal and a ilatelectrode arranged to contact at a plurality of marginal portions withan air gap at the central areas, an auxiliary plate of electricallyconducting material arranged adjacent said electrode opposite to saidcrystal, and spring pressure means for urging said auxiliary plate,electrode and crystal into contact, a plurality of said marginalportions having openings therethrough and said auxiliary plate beingprovided with relatively sharp nger portions extending through saidopenings and adapted resiliently to engage said crystal and maintaindirect electrical contact therewith.

5. In a piezo-electric oscillator assembly having a casing and a crystalsandwiched between a pair of plate electrodes therein and arranged to becontacted at marginal portions by the electrodes with an air gap at eachside of the crystal over its central area, a relatively thin resilientauxiliary plate of electrically conducting material arranged adjacentthe surface of each electrode on the side respectively opposite to thecrystal, and spring means for compressing said auxiliary plates,electrode plates and crystal, each of said auxiliary plates being urgedinto contact at its central area with its respective electrode andhaving at the outer edge spaced bent fingers adapted to extend throughopenings in the respective said marginal portions and presenting arelatively sharp extremity resiliently engaging said crystal to maintaindirect electrical contact therewith.

6. In a piezo-electric oscillator assembly having a crystal and a plateelectrode arranged in contacting relation therein, an auxiliary memberof electrically conducting material arranged adjacent said electrode onthe side opposite said crystal, and spring means for electricallycornpressing together said auxiliary member, electrode and crystal, saidmember having a part adapted resiliently to engage a marginal portion ofsaid crystal and to maintain direct electrical contact therewith.

LOUIS R. MORSE.

